In a wide variety of applications there exists the need for a product which will thicken or gel organic based formulations. To meet this need, several gelling agents for organic solvents are available on the market. These generally include colloidal particles (such as silica), metallic soaps (aluminum soap), and cellulose derivatives that require polar cosolvents.
In co-pending application Ser. No. 222,660, entitled ESTERS OF POLYMERIC HYDROXYPROPYL CARBOHYDRATES AND METHOD OF USING SAME AS GELLING AGENT FOR ORGANIC SOLVENTS, filed on Feb. 1, 1972 and assigned to the assignee of the present invention, now U.S. Pat. No. 3,824,085, issued July 16, 1974, there is described and claimed a gelling agent and process for making same. The process of said co-pending application involves the use of hydroxypropyl cellulose and starch esters, specifically the acetate and laurate esters. The process is quite satisfactory and the hydroxypropyl carbohydrate esters are capable of gelling a large number of organic solvents.
In accordance with the present invention a new composition and process has been discovered which comprises the hydroxypropylation, methylation and acetylation of cellulose in one continuous process to produce methyl hydroxypropyl cellulose acetate, a water insoluble gelling agent for organic solvents. More specifically, the process of this invention involves the simultaneous hydroxypropylation and methylation of cellulose with the continued derivatization of cellulose into acetate. The commencement of the acetylation process prior to the cessation of the hydroxypropylation process eliminates the isolation and recovery of the methyl hydroxypropyl cellulose. As a result, the product is formed in one continuous process.
The preparation of this new polymeric carbohydrate derivative is economical, based on both material and processing costs. The reactions are run under mild conditions, with only a closed reaction vessel required.
Thus, one of the principal objects of the present invention is to provide a new polymeric carbohydrate derivative capable of gelling organic solvents. Another principal object of this invention is to provide a gelling agent for organic solvents that is water insoluble. Still another object is to provide a method of making a gelled organic solvent from methyl hydroxypropyl cellulose acetate. Another object is to provide a method of making an improved gelling agent for organic solvents by the simultaneous hydroxypropylation and methylation of cellulose and continuing the cellulose derivatization by acetylation. Other objects and advantages will become apparent hereinafter.
Gelling of volatile chemicals retards the rate of vaporization allowing only a slow release of vapor. The gelling agent of the present invention is useful in many applications, some of which include gelling jet fuel, soil fumigants, herbicides, paint stripping formulations and cleaning solvents. Some of the organic solvents which the methyl hydroxypropyl cellulose acetate of this invention is capable of gelling include: carbon tetrachloride, toluene, acetonitrile ethylacetate, methyl ethyl ketone, dioxane, dimethyl sulfoxide, dimethyl formamide, pyridine, and benzyl alcohol.